The surprisingly simple chemistry of DuoSkin, temporary tattoos that control your phone

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This tattoo is temporary, but it definitely changed people’s impressions of wearable technology. Discover DuoSkin, an innovation from MIT’s Media Lab and

Microsoft
To research. Metallic tattoos, inspired by trendy body art, allow wearers to use their skin as an interface for smartphones and computers. The product is not yet available for purchase. At this stage, this is the subject of an article that will be presented at a future conference on wearables. That hasn’t stopped tech and fashion journalists from posting a “Sign Me Up.”

DuoSkin touch slider made from gold and silver leaf. (Photo: Jimmy Day)

I see DuoSkin as more than a wearable story. These striking tattoos remind us that the chemistry behind devices in our increasingly connected world.

Ultra-thin smart tattoos are nothing new. Consider the patch from cosmetics giant L’Oréal that monitors exposure to the sun’s UV rays, this temporary tattoo that unlocks your cell phone, and this prototype designed to measure a chemical called lactate, an indicator of fitness and physical performance. , in human sweat.

DuoSkin’s innovation breaks with the specialized and expensive materials of most electronic skin devices, such as conductive carbon or silver ink. Cindy Kao, an MIT graduate student, and her colleagues make tattoos from everyday materials available at craft stores: temporary tattoo printing paper and gold foil. Real gold leaf is available for purchase, but based on the report’s price of $ 10 per pack, Kao and the team likely used an imitation gold leaf, made from a mixture of mainly copper. (UPDATE – Kao confirmed via email that they had indeed used the imitation foil.)

Control devices from the DuoSkin 2D trackpad. (Photo: Jimmy Day)

Gold and copper are both excellent conductors of electricity. They belong to the “metals” section of the periodic table, where the elements have free electrons to move around. Electric current, at its most basic, is made up of electrons moving along a wire. So it makes sense that elements with less confined electrons (metals) make better conductors. Aspiring chemists learn this when they’re still in high school or college, and they’re exposed to several different ideas about how it works at the smaller-than-microscopic level of individual atoms.

Chemistry students are discovering other properties of metals which are useful for these tattoos. Metals are excellent conductors of heat, an important property for the color change sensor. Metals are called malleable, which means they can be hammered into thin sheets (thinness is a desirable quality in a device that is going to be stuck to the skin). Considering all of this, it almost feels like the use of gold foil for skin electronics should have been obvious. But that’s the funny thing about science. Many innovations are only evident in retrospect. With one exception in the field of paper electronics, the MIT-Microsoft team was unable to find another example of gold foil used in this way.

Let’s be honest, though. DuoSkin hasn’t gained media attention just because it’s cheaper than the competition, or because copper is a good conductor of electricity. Kao’s tattoos are strikingly beautiful. They are inspired by metallic temporary tattoos appearing at festivals like Coachella, on Instagram and in street style. Last year I bought a sheet of these tattoos as a gift just because they caught my eye. DuoSkin tattoos are customizable – volunteers who tried them out at MIT were able to design their own tattoos instead of purchasing a one-off device. And they’re easy to wear – volunteers preferred gold leaf tattoos, which can be applied with water, to designs using copper tape, a favorite of the Maker community, like conductive material.

DuoSkin tattoos can detect touch input to control a music app on a smartphone, change color based on changes in body temperature, or transmit data to other devices. I remember the Clapper, folks. DuoSkin is a dazzling and glamorous progress booster.



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